from math import sqrt
def main():

    x1, y1, x2, y2 = map(float, input().split())
    print(sqrt((x2-x1)**2 + (y2-y1)**2))

if __name__ == '__main__':
    main()
 from math import sqrt def main():

    x1, y1, x2, y2 = map(float, input().split())
    print(sqrt((x2-x1)**2 + (y2-y1)**2)) main x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 print(sqrt((x2-x1)**2 + (y2-y1)**2)) print sqrt((x2-x1)**2 + (y2-y1)**2) sqrt (x2-x1)**2 + (y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():

    x1, y1, x2, y2 = map(float, input().split())
    print(sqrt((x2-x1)**2 + (y2-y1)**2)) def main():

    x1, y1, x2, y2 = map(float, input().split())
    print(sqrt((x2-x1)**2 + (y2-y1)**2)) main
from math import sqrt
def main():

    x1, y1, x2, y2 = map(float, input().split())
    print(sqrt((x2-x1)**2 + (y2-y1)**2))

if __name__ == '__main__':
    main()

